Draft-regulating apparatus



March 24, 1931. 1. T. MARV'TIN 1,798,122

DRAFT REGULATING APPARATUS Filed Aug. 17, 1929 CLOSE Frr-rma DAMPER a F '3 i xiv-21:11:22. DAMPER CONTROL BASE STACK CHIMNEY DRAIN PIPE.

34 ALTITUDE 0R PRESSURE Gauea 32 DRAFT GAUGE INVENTOR. 172A 77 MART/N.

GROUND bi wn/6% A TTORNE YS.

Patented Mar. 24, 1931 PATENT QFFICE IRA T. MARTIN, OF SAN FRANCISCO, CALIFORNIA DRAFT-REGULATING APPARATUS Application filed August 17, 1929. Serial No. 386,524.

This invention relates to draft regulating devices as used in connection with furnace stacks.

The objects of the invention are to provide means whereby a better control of the draft in a furnace stack may be secured.

A further object is to provide a means whereby the stack gases from any furnace can be controlled in such a manner as to make the draft intensity in the furnace selective at the will of the operator over a range of draft intensity from a complete sealing of the furnace as a minimum of the highest natural, induced or forced draft available, as a maximum. A further object is to provide a device through the useof which fire hazards can be reduced by the prevention of escaping sparks from the chimney, or stack. A further object is to provide a means of controlling the combustion of fuel in a furnace in such a manner as to reduce to a minimum the formation of soot and smoke and the expulsion of fly ash into the atmosphere.

These objects are accomplished by means 25 of apparatus which will be hereinafter described and claimed.

In the accompanying drawings, Fig. 1 is a general View in elevation of a furnace and stack equipped with and showing one embodiment of my invention, and with portion of the water tank broken away.

Fig. 2 is an enlarged cross section of the stack as seen from the line 2-2 of Fig. 1 showing the positively closing damper.

In the drawings 1 represents a furnace of any desired design, 2 the chimney or stack, 3 aside outlet located preferably above the roof 4 of the building in which the furnace is housed, and extending from the side outlet 3 is a downwardly curved L or return bend 5 11 is positioned at a point beyond the side outlet controlled from below by a rope or chain 12 passing over a wheel 13 secured to the damper shaft 14;. This damper is a solid or imperforate plate 11 as shown in Fig. 2 and seats against an internal flange 15 when closed so as to completely close off or seal the main vertical stack and force all gases to travel through the return bend.

The lower edge of the return bend is pref erably cut off at an angle as shown at 16 so that when water is introduced into the tank through a supply pipe 17 its level may be raised so as to gradually close the end of the return bend.

Supply pipe 17 has a control valve 18 conveniently located at its lower portion accessible to the furnace man or engineer in charge, and at its upper end it extends into the return bend 5 as indicated at 19 and is'provided with downwardly directed spray nozzle 20 which may be controlled by a valve 21.

Supply pipe 17 also has a branch 22 directed into the tank outside of the stack controlled by a valve 23.

In line with the lowest working water level 24 ordinarily used in the tank is an outlet pipe 25 connected to two water level control pipes 26, 27 the latter connected to a short standing extension of pipe 26 at a point 28 above the outlet pipe 25 in line with the highest water level to beused indicated by the dotted line 29 and at which level the lower end of the return bend is completely submerged.

Pipe 26 is valved at 30, but overflow pipe 8 27 requires no valve. The extreme upper end of pipe 26 is open at 26 to prevent overflow pipe 27 acting as a siphon.

Tapped into the drain pipe 8 is a small pipe fitted with a pressure gage or altitude 90 meter 32 suitably graduated to indicate the level of water in the tank, or the free space between the water level and lower end ofstack return bend 5, suitable valves are supplied for shutting off this instrument when not being used.

Also tapped into drain pipe 8 is a pipe 33 suitably valved as indicated, and which pipe may be used for the purpose of injecting air, chemicals, neut alizing or purification agents into the tank if desired, as in some cases the stack gases develop an excessive acid condition of the water which may be counteracted by injecting a strong solution of an alkali, or the tank and pipe may be protected by injecting protecting oils such as petroleum or fish oil to form a coating on the inner surfaces of the tank and drain pipe. Of course these agents may be introduced by any other convenient arrangement of piping if desired.

A stack draft gage of conventional con struction is indicated at 34 for guidance of the attendant in maintaining the draft desired.

In ordinary furnace installations the upper end of the super-stack 2 is open, but in installations where forced draft is used or the I through the liquid level control pipe '26. The

fire is then kindled and maintained at a slow rate'of combustion until the furnace tempera ture is-built upto an effective point of combustion, the unburned gases passing up through the base stack, or chimney2, through the side outlet 3 and return bend 5, discharging against the surface of the water in the damper tank and escaping freely through the open endof the damper tank.

As the fire continues to burn and the heat generated in the furnace increases, the velocit-yof air through the furnace will naturally increase due to the rise in temperature of the escaping chimney gases. When such increased velocity reaches the point of maximum :desired velocity, indicated by the draft gage 32,-the water level in the damper tank is raised until the draft-intensity is retarded by the lessening'of the distancebetween the end of the return bendand the surface of the liquid. Such procedure affords a perfect draftcOntroL-or, velocity control of the gases, passing through the furnace up'to and ineluding the maximum draft intensity available due to the vertical height of the diseh'argeend of the return bend above the fire.

The free air openings into the furnace proper, which may be termed the grate openings, 'a-re preferablyproportioned to admit the'projper amount-ofair tomaintain-the most eflicient rate of combustion with theavailable draft intensity or velocity due to the normal setting, or position of the regulator.

.Shou'l'd' itbecome'necessary to drive the furnace to acapacity greater than its normal rating, damper 11 may be given a full opening, the water level in tank raised to seal the end of the return bend, and the column of heated gases allowed to pass directly into the superchimney 2", said superchimney being of a height to create the greatest desired draft intensity or velocity of air through the furnace; this maximum intensity being determined by the overload capacity of the boiler; or other apparatus of which the furnace is'made a part:

In practice there may exist a material difference in draft intensity between that available, when the sol-iddamper is closed and when it is open. Such widely varying draft conditions are again delicately controlled by means of the liquid damper.

In this case the gas travel, through the return bend 5 is reversed and instead of the unburned or hot gases escaping through the return bendyc'oldiair is admitted to thechimney through the return bend and, again, the amount of air admitted tothe superchimney through return bend is controlled by opening or closing the effective aperture thereto by means of the liquid control in the damper tank 6, thereby affording an extremely sensitive check damper control.

In installations where sparks are a menace, valve 23 is closed, valve 21 opened'and a constant spray of water caused to spread across the open end of the bend so that all sparks will be extinguished; When running the spray, valve on pipe 26 is kept fully open if the whole fluecapacity of the bend is required, or else' valves '18 and 30 may be ad justed to hold the'water level at any point desired and as indicated on the gage-32.

In considering my invention as above clescribed it will be seen to compriseacoopera tive arrangement of draft creating and control elements whereby every'degree of draft from the maximum afforded by the superstack to zero through complete closure may be had or maintained, and while I am fully aware of prior attempts to utilize the water tank principle of stack draft control as -evidenced in the following United Statespatents and others:

Benn, No. 82,277 .Hainzl, 627,614 Mendenhall, 134,301; Just, 958,131; TVright, 228,431; Anderson,1,34c1,872; Smith, 391,658.

I-also know as'a practical engineerdesigning and installing stack draft equipment for years that until my apparatus was developed no-satisfactory apparatuswas obtainable for large plants, that none ever used the combination of superstack and return bend and hence were limited to the maximum dra-ft'of the bend elevation and as it is impracticable to put this on the upper end of a tall stack a high draft could not be had, nor was any such apparatus equipped with a dampercn a'continuation of the stack whereby the high draft'could' be shunted over into the return bend. Nor was there ever any use made of a solid or tightly closing plate damper in connection with the side outlet, nor any means of using the return bend as a cold air inlet or check draft to the main stack, nor was any such return bend provided with a slanted lower end for more gradual closure as the water level was raised, nor tank filler pipe arranged as a spark spray in the return bend, nor any multiple pipe system for controlling water to various levels. Nor means for determining the water level at all times, nor means of treating the water for acid or otherwise, and all these features are of great importance in a practical apparatus.

The water level-control pipes, drain, and other details of my invention are not the result of mere chance, as I have tried other arrangements without success or which worked for a while and failed at critical times, for instance floats in the tank were used to control the water level, but as great quantities of soot and accumulation sometimes build up on top "of the water and the water is sometimes far from quiet such floats have been found impracticable, also on account of corrosion by reason of the sulphuric acid formed in the tank. Filling the tank through the drain pipe was abandoned, for the reason that upon drop in the supply pressure through excessive use in the building the tank water being elevated above the building would back up into the line and come out of the fixtures. These and many other faults have been overcome by my improvements so that installations made by me in various large plants have given universal satisfaction and effected maximum economy in fuel consumption, and therefore I claim:

1. Furnace draft control apparatus com-, prising a smoke stack, a side outlet thereon at a point below the top of the stack provided with a downwardly extending elbow 'bend open to atmosphere at its lower end, a water tank into which said bend extends, means for controlling the water level in said tank to seal or open the end of said bend, and means for closing and opening the stack at a point beyond said side outlet.

2. Furnace draft control apparatus comprising a smoke stack, a side outlet thereon provided with a downwardly extending elbow bend open to atmosphere at its lower end, a water tank into which said bend extends, and means for controlling the water level in said tank to seal or open the end of said bend, the lower end of said bend terminating at an angle with the surface of the water.

3. Furnace draft control apparatus comprising a smoke stack, a side outlet thereon at a point below the top of the stack provided with a downwardly extending elbow bend open to atmosphere at its lower end, a water 65 tank into which said bend extends, means surface of the water.

IRA T. MARTIN. 

